The current invention relates to improvements in workholding devices and in V block design in particular. V blocks have been in use in the machine tool industry since at least the 1800""s. They are used for holding parts for machining or inspection. Typically a V is machined or ground centrally in a block which has provision for accomodating a horse shoe style clamp to secure the part in the V. More advanced designs enable the block to be held on up to five sides. Nonetheless, the prior art suffers from numerous shortcomings which include low holding power, marred workpieces, bent screws, a high profilexe2x80x94which creates tool interference and a lack of versatility.
The screw actuated quill of a lathe""s tailstock requires a close tolerance bore in accurate alignment with the headstock. Errors in the vertical alignment are not easily corrected. The clearance between bore and quill and the wear of same is an issue of concern. The stroke depth of the tool is quite limited and the operation of cranking the handle is slow and tedious, especially for xe2x80x9cdeepxe2x80x9d drilling. Additionally, thru the tool coolant drills require special coolant adaptors as the back of the tailstock is xe2x80x9cclosed offxe2x80x9d by the actuating screw.
The current invention seeks to overcome the disadvantages of the prior art and offer additional advantages as will be seen.
In 1895 Thielcher discloses a V type jig in U.S. Pat. No. 550,767 in which the work is secured by axe2x80x9cstrapxe2x80x9d secured by screws into threaded lands on either side of the V. The inverted nature of this jig and the inaccessibility of the work limits the tool to cross drilling applications on a workpiece. In 1906 Blazej (U.S. Pat. No. 810,319) shows a V block having tangent contact drill guide being vertically adjustable by legs straddling either side of the block. Screws on either side of the block secure the position. This prevents turning the block on it side for additional operations. Additionlly the straps cannot exert any considerable clamping force on the work by nature of its design. And in fact, Blazej reverts to a more conventionl horse shoe clamping arrangement on the opposite V block segment. Blazej also teaches the use of a threaded rod connecting V segments. An arrangement utilized in the lathe embodiment of the current invention.
Bryant (U.S. Pat. No. 1,535,570) teaches a V block having threaded holes on the lands on either side of the block to secure and position the V shaped workholding clamp. The threads do not extend thru the block and limit workholding to the V cavity. Additionlly, the clamp has a high profile which may interfere with machining operations. Furthermore, small diameter workpieces are located at the bottom of the V making it less accessible to a cutting tool. And, the clamp will not allow the block to be held on the clamping side.
U.S. Pat. No. 2,543,140 to Vickerman shows a hand wrench having a tangent clamping arrangement with a reversible jaw bearing some resemblence to the current invention.
The patent to Durfee U.S. Pat. No. 2,932,995 bears the strongest resemblence to the current invention. He shows a block having a single central V and flat base (although both are relieved). Additionally, he also shows threaded holes in the lands adjacent to the the V. He also illustrates an I shape tangent plate which is presumably secured at its ends to the block. In addition he also discloses the use of a V liner. This design however, lacks a salient feature of the current inventionxe2x80x94the guide pins secured in the tangent clamp plate and the counterbore feature which recess the securing screws permitting turning the fixture on any side. Additionlly, the threaded holes in Durfee"" design are not threaded completely thru the block limiting the tool to holding the work within the V cavity.
The Crandall U.S. Pat. No. 3,423,885 teaches a V block with threaded holes adjacent the V cavity securing keyway style clamps and having sine bars secured to the corners of the block. The keyway clamps lack the fixed guide pins of the current invention and the securing screws are not recessed. Additionally, he utilizes different size clamps for different size workpieces, and the threaded holes do not go thru the block, limiting the tool to holding work within the V. The sine capability of the current invention utilizes removable sine bases which are only used when required. The ability to remove the base results in a smaller dimension which can be a consideration when holding the block in a vise, and it results in greater holding power on a magnetic chuck with the flat surface making full contact with the magnetic chuck. Additionally, Crandall doe not teach the use of a Y axis sine bar which enables producing angular features other than 45 and 90 degrees.
Irwin discloses an aligned split V block fixture in U.S. Pat. No. 4,445,678. This application is achieved by a different method with the current invention. He also shows threaded holes opposite the V with a clamping arrangement very similar to Bryant. Additionally he utilizes V liners similar to the tailstock embodiment of the current invention, except his liners fit in a step. The patent to Schwarz U.S. Pat. No. 4,579,322 discloses a cable vise that has clamping arrangement bearing resemblence to the current invention. The Jaskolski U.S. Pat. No. 4,650,379 divulges a multi-pin V fixtures with flat sides joined by dowel pins and having recessed screws securing the fixture as with the current invention. However, Jaskolski utilizes a multi-v arrangement and reverts to set screws to secure the work. Additionlly, the multi-V arrangement sacrifices the versatility and number of operations that can be performed as with the single V-cavity fixture.
The patent to Abernathy U.S. Pat No. 4,790,695 has similar features to the current invention. He shows a multiple level modular fixture with drill bushings in a clamping plate having guide rods aligning the various members. The guide rods are threaded at their ends and protrude above the surface of the fixture. While the workpiece may be drilled in more than one plane it is rather a cumbersome fixture geared to production drilling of parts and it could not be inverted or held in a vise for use on various machines.
None of the prior art achieves the versatility of operations and range of workpieces that may be accomodated by the current invention. And none suggest any uses beyond merely workholding.
It is therefore an object of the current invention to provide a workholding V fixture that can hold round, square, hexagonal, rectangular, threaded, or irregular parts. It is an object of the current invention to provide a workholding device that can hold multiple workpieces. It is another object of the invention to hold a workpiece securely for machining. Another object is to provide a non-marring grip. It is yet another object to provide a workholding device that can be held on any side for machining. A further object is to provide a low profile so as to facilitate machining by minimizing tool interference. It is still a further object to provide a versatile device capable of holding workpieces to replicate itself and its accessories, and further that can be adapted to accomplish a range of tasks beyond merely workholding which include punching parts, dressing diamond wheels, sharpening very small and very large drills, performing deep hole center drilling, generating radii on a part and centerless grinding workpieces. And another objective is to extend the clamping and linear motion concepts of the invention to replacing the screw quill arrangement on the tailstock of a lathe.
The current invention is comprised of a cast iron or steel block having a central V machined parallel to a flat base. On the lands adjacent to either side of the V area are a series of holes. Typically two reamed thru holes are laid out symetrically along each land.
A plate or tangent clamp with matching holes to the V block is utilized to secure the workpiece. The tangent clamp has pins pressed into the plate matching the reamed thru holes in the block. The pins may be internally threaded. Counterbored holes in the plate match the threaded holes in the block permitting the screw heads to be recessed allowing the device to be held on any side. The plate may be utilized on either side of the block to secure a workpiece. An alternative means of securing the work is a matching V clamp having pins pressed or otherwise secured into the lands on either side of the V corresponding to the reamed holes in the block and likewise having counterbored holes corresponding to the tapped holes in the block to accomodate and recess screw heads. This arrangement is utilized for producing parts with symetrical features.
A number of accessories extend the range of workpieces the block may hold or allow other operations to be performed. Magnetic parallels allow smaller parts to be held in the fixture. Another method to accomodate smaller work is to utilize a square workpiece which has a step milled on opposing sides, thereby resembling the letter W.
In addition, sine bar bases (either X,Y or Z axis) may be secured to the block enabling the production of angular features on a workpiece.
Partial length clamps may be utilized to accomodate headed or special workpieces. Keyway clamps facilitate machining along the axis or chamfering of workpieces.
A center locater in conjunction with a magnetic base facilitates rapid setups on a drill press.
A clear window clamp may be utilized for part inspection.
A length of filler V stock drilled to accomodate a diamond dresser on one end and a knob on the other in conjunction with a bearing in the cover produces accurate linear motion so that a grinding wheel can be dressed. The reciprocating V member may accomodate a dovetail slide fixture facilitating the sharpening of micro size drills. The V clamp double V arrangement is utilized for resharpening large drill bits.
Another accessory consists of a cylindrical socket whose female bore accomodates workholding collets. The socket has a series of holes about the circumference. A pin in the cover enables indexing of the part. Outboard beatings permit spin grinding of a workpiece.
A motor may be mounted atop the cover.
A series of blocks may be assembled with the aid of a male V member to create a lathe for center drilling workpieces. The tailstock member traverses along the male V by means of a cover bearing and lever actuated rack and pinion.
A gear train, bearings (-supporting a live shaft), and a motor may be employed to allow centerless grinding of workpieces.
The tangent pin clamping concept may be employed with a V shaped quill in the tailstock of a lathe.